CHAP. IV. OF THE RELATION BETWEEN ANTS.

Of those insects that live solitary, their generation, their private habits, the metamorphoses they undergo, and their mode of living under each variety of change, their artifices in attacking their enemies, and the art with which they construct their habitations, forms their whole history. But the history of insects, living in extensive societies, is not limited to any remarkable proceedings, or to the display of any particular talent; it offers us a series of links depending upon common utility, equality or superiority of rank, and the part each individual is called upon to perform in the society of which it is a member. These several links denote a bond of union between the different members, that could not be preserved without the intervention of language. Under this term I include, whatever means they possess of expressing their desires, their wants, and even their ideas, if we may be allowed to give this term to the impulse of instinct. It would be difficult to explain in any other manner, that centering of all wills to one purpose, or that species of harmony which so universally reigns in their institutions.

We have already made known several facts, proving the sociability of ants, whilst speaking of the education they give to the little ones of another mother; of their conduct towards the males and females; and of the labours they undertake in common in the construction of their abode. But these are only to be regarded as isolated facts, which do not show in what the true secret of this harmony consists; and it is, doubtless, only by examining their conduct under this point of view, and with much greater attention, that we can hope to acquire any knowledge of the manner in which these diminutive republics are constituted. For this end, we shall first study, daily, the relations of ants one with the other; relations under which we have not yet considered them, and which will merit a few moments’ consideration. Let us take, for this purpose, the most simple and ordinary traits in the life of these insects. The guard or sentry of the ant-hill will furnish us with the first proof of their social relations.

We could, without doubt, irritate ants on the surface of the nest, without alarming those in the interior, if they acted isolately, and had no means of communicating their mutual impressions. Those who are occupied at the bottom of their nest, removed from the scene of danger, ignorant of what menaces their companions, could not arrive to their assistance; but it appears, that they are quickly and well informed of what is passing on the exterior. When we attack those without, the most part engage in their defence with a considerable degree of courage: there are always some, who immediately steal off and produce alarm throughout their city; the news is communicated from quarter to quarter, and the labourers come forward in a crowd, with every mark of uneasiness and anger. What, however, is highly worthy our remark is, that the ants, to whose charge the young are confided, and who inhabit the upper stories, where the temperature is highest, warned also of the impending danger, always governed by that extreme solicitude for their charge, which we have so often admired, hasten to convey them to the deepest part of their habitation, and thus deposit them in a place of safety.

To study in detail the manner in which this alarm spreads over the ant-hill, we must extend our observation to the individuals of the largest species: the Herculean Ants, who inhabit hollow trees and who quit them only in the spring, to accompany the males and females, have very much assisted me in this object.

The labourers are from five to six lines in length; the winged individuals are also proportionably large: they may be frequently seen running about the trunk of an oak, at the entrance of their labyrinths. When I disturbed those ants that were at the greatest distance from their companions, by either observing them too closely, or blowing upon them lightly, I saw them run towards the other ants, give them gentle blows with their heads against the corslet, communicating to them, in this way, their fear or anger, passing rapidly from one to the other in a semicircular direction, and striking several times successively against those who did not put themselves in instant motion. These, warned of the common danger, set off immediately, describing in their turn different curves, and stopping to strike with their heads all those they met on their passage. In one moment the signal was general, all the labourers ran over the surface of the tree with great agitation, those within receiving notice of the danger, and probably by the same means, came out in a crowd and joined this tumult. The same signal which produced upon the workers this effect, caused a different impression upon the males and females; as soon as one of the labourers had informed them of their danger, they sought an asylum, and re-entered precipitately the trunk of the tree;—not one thought of quitting its temporary shelter, until a worker approached and gave them the signal for flight. The solicitude of the labourers in their favour, is manifested in the activity they display, in giving them advice or intimating to them the order for their departure; they redouble then the above signals, as if conscious of their understanding their intent less readily than the companions of their labours: the latter understand them, if I may use the expression, at half a word; however, there are cases, where there is a necessity for their repetition, as the following example will prove. Its detail may appear minute, but as it is demonstrative of the ants possessing some kind of language, I hope to ground my excuse on the importance of the subject.

The feet of the artificial ant-hill, or ruche, were plunged in vessels constantly filled with water; this expedient, originally adopted to arrest the passage of the ants, proved to them a fruitful source of delight, for they there slaked their thirst (like butterflies, bees, and other insects), during the great heat of summer. One day, whilst they were assembled at the foot of the ruche, occupied in licking up the little drops which filtered between the fibres of the wood, (which they preferred to the taking it from the bason itself,) I amused myself in disturbing them. This trifling experiment gave rise to a scene which appeared conclusive. The greater part of the ants immediately ascended the leg of the ruche; a few, however, remained, whom my presence had not alarmed, and who continued carousing. But one of those who had regained the ruche, came back and approached one of its companions, who appeared fully absorbed in the pleasure of drinking; it pushed it with its mandibles several times successively, raising and lowering its head alternately, and at length succeeded in driving it off. The officious ant then reached another, who was engaged in the same office, and endeavoured to drive it off also, by striking the abdomen behind; but seeing that it did not appear to, or would not, understand its meaning, it approached the corslet, and gave it two or three blows with the end of its mandibles. The ant, being at length apprised of the necessity of withdrawing, passed precipitately to the bell-glass; a third, warned in the same manner, and by the same ant, quickly regained its habitation; but a fourth, who remained alone at the water’s edge, would not retire, notwithstanding numerous proofs of the solicitude of which it was the object:—it appeared to pay no attention to the reiterated blows of its friendly monitor, who at length seized it by one of its legs, and dragged it away rather roughly. The toper, however, returned, keeping his large pincers extended with all the appearance of rage, and again stationed himself to quaff the delightful beverage; but its companion would give it no quarter; coming in front, it seized it by its mandibles, and dragged it very rapidly into the ant-hill.

These observations show us in what manner the ants are understood, when they wish to give friendly notice of the danger with which they believe themselves threatened. Let us now pass on to the means they employ for directing their course in their journeys and emigrations.

2. Of the Manner in which Ants are guided in their several Excursions.

An ingenious idea, offered by a man of celebrity, is sometimes sufficient to fix the opinion of naturalists, who would rather adopt his idea than take the trouble of examining for themselves. It is thus, that M. Bonnet, in comparing the odour from ants to those threads which caterpillars, living in a republic, leave after them, has concluded, that these insects are guided only by smell. He remarked, that he could arrest the passage of ants, by passing his finger occasionally across their path; but he had not perhaps reflected, that the odour from his hand was a sufficient barrier to their progress: this experiment, however, is not always attended with the same success. Some ants are stopped at the moment, by the new sensation they experience, but the greater part pass boldly the space, where we should have imagined the invisible traces of their passage interrupted. I put them to a more difficult trial, by digging around their nest a ditch several inches in depth. They appeared at first to hesitate as to their movement, but they did not forget the direction of their ant-hill, knowing the way of returning to it, although the road in this part was completely destroyed. When they had traversed this furrow, they often returned behind, exploring the ground, as if to observe their route for the purpose of again remembering it.

Why exclude sight, touch, and memory, from the part they take in regulating the conduct of ants? Objects, which by us would be passed unnoticed on account of their diminutiveness, may be very remarkable with respect to them. We may be convinced by what follows, of the fidelity of their memory, and of the subtilty of their senses.

If ants had nothing to direct them in their journeys but the odour they leave after them, how could they possibly ascertain their route when continued rains have soaked the ground they are to run over, and effaced the traces of their steps, or when violent winds have dispersed their emanations. One would think they would be thrown in disorder; this however is not the case: they find again the places they before frequented, go considerable distances to seek provisions; and know every route which leads to the ant-hill.—I do not deny that the sense of smelling may be one of the means they possess in tracing their route, but there are circumstances in which sensations in that way would throw them into the greatest perplexity. We well know that several wild deer will deceive the best dogs of chace, by retracting their steps in their several turnings and windings;—the ants would be deceived in like manner by the emanation from their companions, if they possessed not the knowledge of places, from the inspection of objects, the memory of localities, or from other resources, to us unknown.

I have often amused myself by dispersing in my chamber the fragments of one of their nests. I expected to see the ants follow each others’ track, and move in one unbroken chain (as we find to be the case with caterpillars) to seek a place of shelter; but this was not the plan they followed; they diverged on all sides and took a thousand different routes: each pursued his own way. They encountered each other at different points without appearing to have the slightest idea of any clue that might direct them. I saw them for a long time wandering about at random before they found a place where they could all assemble. One of them having discovered in the flooring a little chink through which it could glide into a darkened cavity, returned to its companions, and, by means of certain movements with its antennæ, imparted to them the joyful intelligence. It even directed some by accompanying them to the entrance of this aperture, and these, in their turn, served as guides to the rest. Every time they met, they stopped and struck each other with their antennæ in a very remarkable manner, and appeared fully instructed of the route they should take. In this way, the whole of this busy group were securely lodged in the same place.

If we could remove an ant at the moment of her discovering a repository of confectionary, &c. none of her companions would be able to arrive there; since it is not her traces that conduct them to the spot, she is under the necessity of returning to the ant-hill and bringing off her companions.⁠[1] What difficulty has she not in finding her route? how many times does she not stop in going to, or returning from this land of promise? She endeavours to discover the places that lay in her former route; she is seen to halt almost every instant, until she happens to meet with some visible or palpable clue, as the extremity of a road, or the base of a wall, which she can follow without hesitation. Should she fall in with any of her associates from the nest they put her in the right way by the contact of their antennæ.—This method of guiding their companions is not practised by every species of ants; for some employ, under certain circumstances, a process more mechanical and less rapid than the fugitive signs of which the antennæ are the organs. This is the subject upon which we shall now touch in speaking of their migrations.

3. The Migrations of the Fallow Ants.

Ants are now and then induced to change their residence. Should it be too much in the shade, too humid, too exposed to the attacks of passengers, or too contiguous to an enemy’s quarters, thus rendering it unsafe as well as unpleasant, they leave it to lay the foundation of another in some other place. This I have denominated migration, the term colony offering no sufficiently just idea, since we do not speak, in this instance, of a portion of the metropolis, but of a whole nation removing to a new city. However, I shall occasionally employ it under the same acceptation. Do ants determine upon the propriety of removing to another abode after general deliberation? How do they appoint the place of rendezvous, and the day of departure? These questions, and the facts connected with them, have hitherto escaped the attention of naturalists; although several (Bonnet, Latreille, Bomare) have sufficiently spoken of a practice common enough among ants,—that of their carrying each other; yet they were ignorant if they should attribute this conduct to the sickness, infancy, or old age of those ants that were borne by their companions.

I was equally ignorant of their intention in this respect; but having one day deranged the habitation of a colony of Fallow Ants, I perceived they had changed their domicile. I saw, at the distance of ten paces from their nest, a fresh ant-hill, which communicated with the old by a path struck out in the grass, along which the ants were passing and re-passing in great number. I remarked that all those going towards the new establishment were loaded with their companions, whilst those moving in a contrary direction were running one after the other⁠[2]⁠: these were no doubt returning to the old nest, to seek inhabitants for the new. This proved an additional source of knowledge.

From that period, I put several of these republics to the same proof. I destroyed so often the roof of their underground city, that I completely succeeded in driving them from their residence. The first and second time they repaired the breaches I had made; at the third they began seeking an asylum less exposed to such accidents. I then observed one of the labourers leave the nest, carrying one of its companions suspended by its mandibles: I followed it until it reached the border of a subterranean cavity, in which it deposited its burden.

The number of these carriers or porters, at first but trifling, increased each moment. I only noticed, at the commencement, two or three in the path; but, after they had carried off several others to begin their operations at the new ant-hill, one part of the colony went, in their turn, to the ancient nest, and thence drew, as from a nursery, subjects for the new city. To judge with what ardour they were occupied with their colony, it was only necessary to watch the arrival of new recruits to the natal ant-hill. They approached in haste several ants, caressed them individually with their antennæ, drew them forth by their pincers, and actually appeared to propose to them the journey. When they saw they were disposed to set off, I observed them seize them by their mandibles, and whilst the one destined to be the porter or carrier turned about to take up the other it had brought over to its views, the latter rolled itself up, suspended from the neck of the former. All this took place in the most amicable manner, passing and repassing the antennæ over the head of each other, with movements little varying from those when they are about to take their food. It sometimes, however, happened, that those who were desirous of the change seized the other ants by surprise, and dragged them out of the ant-hill, allowing them no time to offer resistance; they bore them off with great rapidity, and when they had nearly arrived to their new habitation, the ants suspended by their mandibles unrolled themselves, and quitted their conductors.

The number of recruits increases always in rapid progression; the path communicating with the two cities is filled; the natal ant-hill is covered, and its surface is the theatre of their excursions and their enlevemens: they never return to the new colony, without bringing back some pledge of their dispatch or address.

My glass frames often permitted me to see what occurred in the interior of ant-hills during the emigration, for when the labourers espied any issue that had escaped my vigilance, they profited by it to seek another asylum. They spread themselves at first separately over the floor, and observed all the corners of my study, hoping to discover an asylum in which they might be sheltered: this obtained, they began to recruit. That ant which had found a place of safety, went immediately to seek its companions, one after the other, on the floor, then in the ant-hill: but it was sufficient, by simply taking away at the time the first recruit, to stop the emigration, at least until some other ant had discovered an equally convenient retreat.

The recruiting continued several days; but when the whole of the labourers knew the route to their new habitation, they ceased to carry each other. They had by this time constructed large vaulted chambers, avenues, and lodges; they first brought off their pupæ and larvæ, then the males and females. When the removal was complete, they for ever abandoned the artificial ant-hill, and the road which led to it.

But upon opening the shutter of my ruche whilst the emigration on the exterior was in full activity, all appeared tranquil within; those recruiting, arrived at the very gate of the ant-hill, but the ants, who were not immediately the object of their search, paid no attention to their proceedings; they continued, as usual, their ordinary avocations, and did not appear to suspect what was going forward so near them. Thus, these enlevemens produce no sensation but in the very spot where they take place, which proves, that the ants do not take counsel of the whole republic when they feel inclined to change their abode. That ant which discovers a situation favourable to the establishment of an ant-hill, conducts its companions to it, and these, in their turn, go and seek new inhabitants. It now and then happens that several workers undertake at the same time to found a new city, and conduct there the whole colony, which gives place to a temporary existence of several ant-hills; but these insects are soon aware of this division, and do not delay, in the last recruiting, bringing the whole colony into one nest.

When the ants are displeased with the city they have chosen, they quit it for a third, and pass sometimes even to a fourth, where they definitively fix. We even see them very frequently return to the ancient nest before being fully established in the new. The recruiting then takes place in a contrary direction, and the couples meet each other in the same road, but the last has always the advantage over the preceding emigrations.

When the new ant-hill is at a considerable distance from the old, the ants commonly establish some intermediate residence, in which they deposit the recruits, the larvæ, the males, and the females, which they are unable to carry in one journey to their proper destination. I have seen several of these relays established upon the same route; they consisted of cavities pierced in the earth, containing sufficiently spacious apartments, generally covered with fragments of straw, and resembling small ant-hills. We might there observe some sentinels doing daily duty, that is to say, opening and closing the gates of the ant-hill morning and evening; sometimes these asylums become little colonies, which maintain a close connection with the principal ant-hill; they are different habitations, common to the same ants, serving them for places of refuge on any derangement of what we might term their capital.⁠[3]⁠

I have often seen in fir-forests, very large ant-hills contiguous to each other, communicating together, like cities of the same empire, by regular tracks:—these tracks are sometimes as much as a hundred feet in length, and several inches in breadth; they are not produced by the passing and repassing of the ants, several thousands of whom are in motion each day from one ant-hill to the other, but are excavated by the ants themselves. I have often seen these insects occupied in establishing them, or in giving them greater breadth. This art belongs exclusively to the Fallow Ants; but the recruiting is common to them, with the Herculean, Ethiopian, Ash-coloured, the Sanguine, and the Mining Ant. That very valuable gift of being directed in their movements by means of the antennæ, of which we have before spoken, is in use among the Brown, the Yellow, the Fuliginous, and several other ants.

We have one word to say respecting Field Ants, which take a middle place between the two genera we have described, inasmuch as they sometimes conduct themselves peaceably towards each other, and regulate their movements by signs; but what is very remarkable is, the manner in which they take off their recruits; in place of carrying them rolled up and suspended under their neck, they hold them in a contrary direction; they also take them up by their mandibles, but with their head below, and their body raised in the air.⁠[4] It never happens, as had been supposed, that the labourer who wishes to be carried fastens himself by force upon one of its companions. The Brown and Fuliginous Ants, who are not in the habit of carrying each other in their migrations, have recourse, notwithstanding, to this expedient with regard to the males, females, and labourers, lately transformed; which amounts to the proof, that these do not well understand their language, and could not be their own directors.

4. Of the Affection of Ants for their Companions.

The affection between members constituting one and the same family is, without doubt, the just basis for harmony and public good. Even were we not accustomed to regard the actions of insects as mechanical, we could not possibly explain the order so conspicuous among bees and ants, without supposing them endowed with an attachment to their fraternity, which inspires them with that great zeal for the well-being of the colony, with that attention and that devotedness, of which they offer striking examples every instant of their life. With us, intimacy results from some decided preference; with them, this affection has nothing exclusive, offering rather an idea of the patriotism which accords with republican states. Their friendship is never destroyed by the shock of contending passions; there is not to be found amongst them either hatred, rivalry, or dissension. What individual is not acquainted with the devotedness of bees for their republic! The females, even of the larger animals, do not defend their little ones with more spirit and obstinacy. Ants yield in no respect to bees: it is well known, that we may divide ants in the middle of their body, without taking from them the desire of defending their domicile, that the head and corslet, although separated from the abdomen, still continue in motion, and that, in this state, the ant will convey the pupæ to their asylum.⁠[5] Thus the great secret of the harmony we admire in these republics rests in their reciprocal affection. It will be enough to bring to remembrance what M. Latreille has mentioned, respecting some ants, who, upon witnessing the suffering of their companions, whose antennæ he had cut off, dropped from their mouth, upon the wounded part, a little transparent liquor, of which they knew, perhaps, the full virtue. I have no equally affecting instances to relate. I shall, however, mention two, which prove the lasting attachment of members of the same republic, and the desire that their associates might also participate in their pleasures.

I took, in the month of April, an ant-hill from the woods, for the purpose of populating my large glazed apparatus; but, having more ants than I had occasion for, I gave liberty to a considerable number in the garden of the house where I lived. The latter fixed their abode at the foot of a chesnut tree. The former became the subject of some private observations. I noticed them four months, without allowing them to quit my study; at this time, wishing to bring them nearer to a state of nature, I carried the ruche into the garden, and placed it at ten or fifteen paces from the natural ant-hill. The prisoners, profiting by my negligence of not renewing the water which blockaded their passage, escaped, and ran about the environs of their abode. The ants, established near the chesnut tree, met, and recognised their former companions; fell to mutual caresses with their antennæ, took them up by their mandibles, and led them to their own nests: they came presently in a crowd to seek the fugitives, under and about the artificial ant-hill, and even ventured to reach the bell-glass, where they effected a complete desertion, by carrying away successively all the ants they found there. In a few days the ruche was depopulated. These ants had remained four months without any communication. I placed some Fallow Ants in another artificial ant-hill, the frame of which, in place of lying perpendicular with the table, as in figure 1. was inclined some degrees. This disposition displeased the ants (I know not why), and they established themselves underneath the bell-glass in the materials of their nest, which had been brought with them. It was, however, necessary, to allow of my making any observations, they should remain in the frame, and I hoped to retain them there, by the attraction of heat. For this purpose I brought a flambeau close to the frame, and kept it in the same position, until the glass had acquired a sufficiently high temperature. There were some ants in this place; as soon as they perceived the heat, they began to be animated, manifested their comfort by brushing their head and antennæ with their feet, and ran over, with rapidity, the warm space. When they saw other ants, they approached them, moved about their antennæ with singular quickness, and then immediately left them. They appeared desirous to remount under the bell-glass; they went even to the border of the table, but retained, without doubt, by the mild temperature they experienced in the frame, they often returned to it; they took, at length the measure of mounting into the upper story. I knew enough of the habits of ants to be well aware they were only gone to intimate to their companions this heat, to which they attached such value. In short, I presently saw two descend into the frame, carrying in their mouths two labourers, whom they deposited in the warmest place; they then returned immediately into the upper part of the ruche. The new arrivals, after having warmed themselves, mounted also under the glass, when, in a few minutes after, I saw the whole four re-descend, each bearing another ant suspended by its mandibles. This transport continued in rapid progression, until there arrived, by hundreds, the recruits, with their living burthens, and there remained no longer any ants in the superior part of the ruche. When I ceased warming the frame, the ants regained the glass, but as often as I approached the flambeau, this social proceeding again took place.⁠[6]⁠

These observations, and many others, which I shall not now mention, by showing what interest the ants take in the welfare of their companions, bring to mind those ideal republics in which all wealth should be general, public interest serving as a rule of conduct for the citizens. It belonged only to nature to realize this chimera, and it is only among insects, exempt from our passions, that she thought she could establish this order of things. She has given to ants a language of communication by the contact of their antennæ; with these organs they are enabled to render mutual assistance in their labours, and in their dangers; discover again their route when they have lost it, and make each other acquainted with their necessities. We see, then, that insects which live in society are in possession of a language. In consequence of enjoying a language, in common with us, although in an inferior degree, have they not greater importance in our eyes, and do they not embellish the very spectacle of the universe?